The invention is related to an automatic setup system for television cameras, and particularly to a simplified multichannel automatic setup system located in the camera head for operation with conventional multichannel analog multiplex/demultiplex remote control systems.
Television camera systems typically employ a control system within the camera head, and a multiplexed, remote control system removed from the camera head, to control the various operating parameters of the camera. Operating parameters which are controlled in this manner may include red and blue gain, the red and blue black levels, the iris setting, black stretch, beam optimization, etc. Most, or all, of these operating parameters are controlled via the remote control system, but there are specific parameters such as, for example, the red and blue gain and the red and blue black levels, etc., that also preferably may be controlled locally at the camera head. It follows that typical camera systems provide means for combining the control signals generated at the camera head with the commensurate control signals being remotely applied from the remote control system. Often, to simplify their transmission, the many remotely controlled signals are applied via a multichannel analog time-division multiplex/demultiplex system, in which case, those parameters which are both remotely controlled and locally controlled have the two control signals summed together after the remote control signal has been demultiplexed.
Prior art setup systems have typically employed one capacitor/integrator, or one counter/DAC combination for each automatically controlled operating parameter, to generate, store and retrieve respective error-correcting analog control voltages. In addition, one summing amplifier per channel is used to combine the automatic control voltages with the remote control voltages for each automatically-controlled parameter. Thus in prior art setup control means wherein a plurality, e.g., four operating parameters are automatically controlled at the camera head, then four counters, four DAC's and four summing amplifiers are required, that is, one counter, one DAC and one summing amplifier per parameter.
The most recent prior art automatic setup systems employ digital components wherein, to correct a particular error, the error signal for that parameter is applied to the counter, which supplies resulting digital data therefrom to the DAC. The counter is incremented, whereby the DAC generates an increasing or decreasing analog ramp voltage commensurate with the counter counting up or down, as directed by the nature of the error. The ramp voltage is applied back to the camera circuitry which controls the parameter in question, causing the parameter to ramp up or down accordingly. At the point where the error becomes zero for the parameter being controlled, the control loop is disabled and the counter retains the digital number corresponding to the error correction value for the parameter. In such prior art systems, a successive approximation register has also been used in place of the counter. However, in either system, a counter or register is required for each channel. Thereafter, during the operation of the camera, the counter and DAC continually maintain the corresponding static error correction voltage.
Thus, it may be seen that one counter and one DAC is required for each channel, i.e., each operating parameter which is to be automatically controlled locally at the camera head. In the typical situation of previous mention, four parameters, i.e., red and blue gains, and red and blue black levels are automatically controlled, which requires accordingly, four counters and four DAC circuits.
In addition, television cameras typically require remote control of a larger number, e.g., 12 to 64, operating parameters in addition to the few automatically controlled parameters noted above. Thus, in the case of the four parameters, it is necessary to add the control voltages generated by the remote control system, with the control voltages generated by the four counters and four DAC circuits of the automatic control system. Therefore, since each channel which employs both the automatic and remotely controlled voltages requires a summing amplifier, four of the latter also are required in the above example. It follows that three discrete or integrated circuits are required in each channel of such prior art automatic control systems.
It may be seen that prior art automatic setup control systems are somewhat cumbersome and generally require a redundant combination of components for each channel, and thus for the systems.